This invention relates to a stabilized gate driver which comprises a current source transformer which comprises a primary coil and a secondary coil, and a gate driver unit which comprises a positive auxiliary voltage input and a negative auxiliary voltage input.
When a power semiconductor component, e.g. an IGB transistor, is controlled, it is important to keep the control voltage within certain values. Typically the voltage used for igniting an IGB transistor should not be lower than +13 volts. If the voltage used for controlling the power semiconductor is too low, the power semiconductor will not become completely saturated, which causes additional conducting losses in the power semiconductor. On the other hand, if the gate voltage exceeds +15 volts, the possible short-circuit current increases so much that it is no longer safe to cut it off quickly.
Considering the disturbance tolerance, the gate of the IGBT to be turned off should be rendered to the negative potential with respect to the emitter. This allows to prevent unintentional ignition of the power semiconductor caused by changes in the potential. A suitable range for turning the IGBT off is from about -5 to -15 volts. The turn-off voltage may vary within a wider range than the ignition voltage without interfering with the function of the power semiconductor.
Earlier voltages for controlling the power semiconductor have been generated with a current source transformer the secondary coil of which comprises a middle output. This way we obtain a bilateral symmetric voltage which does not, however, satisfy all the requirements set for controlling the power semiconductor. Since the voltage feeding the current source transformer has not been stabilized, the voltage may often vary too much, which is disadvantageous particularly on the positive side. Furthermore, this renders the structure of the transformer comprising a middle output unnecessarily complicated, which directly affects the costs of the solution in question.